It has been proposed to measure temperature of the human body by way of the ear rather than the mouth or rectum as is most commonly done. Oral thermometers have several noticeable hazards of significant concern to hospital and clinic personnel. If the thermometer is broken in the patient's mouth, as can readily happen with children or elderly persons, the patient may ingest mercury or glass fragments. Further, if thermometers are not thoroughly sterilized between uses communicable diseases may be transmitted from one patient to another. Oral thermometers have the additional disadvantage that they only approximate deep body temperature since the patient may have ingested cooling or warming materials which mask the true temperature.
Oral thermometers are of limited usefulness with infants and rectal thermometers are commonly used. Many serious accidents have occurred due to breakage of the thermometer during such use. In addition, both oral and rectal thermometers are subject to high breakage rates during normal handling. Both oral and rectal thermometers take a substantial time interval to come to temperature equilibrium and the time of valuable health personnel is often wasted during the wait for equilibrium. If the personnel are rushed, inadequate time may be allotted and the thermometer may not have reached equilibrium when the reading is made.
To overcome these difficulties, measurement of body temperature through the ear has been proposed. One such instrument places a thermistor in intimate thermal contact with the interior of the ear. A preferred instrument employs an infrared sensor which detects radiation from within the ear. The infrared sensors are optical instruments requiring an unobstructed "light" path between the sensor and the region where temperature sensing is desired. Such a technique is advantageous since the tympanic membrane is substantially transparent to infrared radiation and the temperature measured is effectively that of the carotid artery which passes in close proximity to the tympanic membrane. Such an infrared sensor is very rapid and comes to equilibrium within seconds. A suitable technique is disclosed in U.S. Pat. No. 3,282,106.
When such a tympanic thermometer employing an infrared sensor is used, it is desirable to insert an end portion into the ear canal so that temperature of the surroundings does not influence the reading obtained. Such a tympanic thermometer is used for many patients much as an otoscope or other ear examining instrument. It has often been the practice to simply wipe the tip of the speculum that enters the patient's ear with alcohol between patients to effect limited sterilization and remove any wax that may have been deposited. Although the likelihood of cross contamination from one patient to another through the ear is very low, it is preferable that a clean speculum be used for each patient.
It is therefore desirable to provide a speculum that is sufficiently inexpensive that it can be disposed of between usages. Preferably, the speculum should have a limited lifetime so that medical personnel do not continue to use the same speculum, and in effect are forced to dispose of it between successive patients. Such a speculum cover should be inexpensive, non-contaminating, non-irritating, and maintain a fixed optical path for the infrared radiation to the sensor.